1. Field of the Invention
The present invention relates to a copying machine, and more particularly to a copying machine having a zooming function wherein an unwanted image is erased by a side eraser equipped with LED heads when a reduction copy mode is selected.
2. Description of the Prior Art
Synchro motors and DC motors are commonly used for driving the copying machine having a zooming function. By controlling the rotating speeds of these motors, a photosensitive drum, a electro static charger located around the photosensitive drum, and a copying process taking place in a development unit and a feeding speed of copy paper are controlled as desired.
Since the rotation of the synchro motor is controlled synchronously with the frequency of a power source, the control of rotation is likely to be inaccurate because of the fluctuating frequencies of the power source. For this reason, a mechanical speed change gear is required, but it results in energy waste because of loss occurring in the power transmission. To compensate for the loss of energy, a large-sized synchro motor must be used, thereby increasing the size of the copying machine, and making the mechanism complicated.
To achieve a small copying machine, it is common practice to use a relatively small DC motor in recent years.
However, a DC motor presents a problem in changing magnification in the copying machines: commonly, magnification is changed by changing a scanning speed of the optical reader system while the copying process is conducted at a constant speed. This requires DC motor for each of the optical system and the copying process. To control the different DC motors, different rotation information is required for generating synchronous control signals. The control system becomes complicated, and an expensive microcomputer having a high quality is needed. As a result, the total cost of the copying machine will be high.